1. Field of the Invention
This invention relates to an electric vehicle which travels with an electric motor driven by a chargeable battery mounted on a vehicle body.
The present application is based on Japanese Patent Application No. Hei. 10-149957, which is incorporated herein by reference.
2. Description of the Related Art
An electric vehicle which travels with a battery produces no exhaust gas, and is silent, thus being suitable for the traveling of a vehicle in an area which should be free from noise or in an environment protection area. In addition, a traveling distance per one battery charging is not affected by traffic congestion, and therefore the electric vehicle is suitable as a short-distance commuting vehicle (so-called xe2x80x9ca city commuterxe2x80x9d).
One of the problems accompanying the electric vehicle is that a traveling distance per one battery charging is short. If no infrastructure for charging batteries is provided, it is difficult for the electric vehicle to achieve long-distance traveling using high-speed roads.
Hence, research effort for development of high-performance batteries which are light in weight and high in charging capacity, development of high-performance motors which are small in power consumption and high in output power, and a recovery brake technique to achieve energy regeneration efficiently, have been conducted and still being proceeded.
However, in spite of the above-described efforts, it is difficult to greatly increase the traveling distance of an electric vehicle, and therefore still there has been a strong demand for an increase in the traveling distance of an electric vehicle.
In view of the foregoing, an object of the invention is to provide an electric vehicle which has a great convenience for short-distance traveling, and is sufficiently useful for long-distance traveling, too.
In order to achieve the foregoing object of the invention, there is provided an electric vehicle having a main battery mounted on a vehicle body; a sub-battery detachably connected to the vehicle body; an electric motor being driven by the main battery and the sub-battery, thereby to generate a traveling drive force and which generates a regenerative brake force at deceleration of the vehicle body; and control means for controlling drive and generation operations of the motor. When the sub-battery is connected to the vehicle body, the control means controls the motor so that (i) the motor preferentially uses an electric power of the sub-battery for driving the motor and (ii) the motor preferentially charges the main battery by a regenerative power generated by the motor.
The electric vehicle is designed as described above. Therefore, with the sub-battery coupled to the vehicle body, the electric powers of the main battery and of the sub-battery can be used to increase the traveling distance of the electric vehicle. In the case where it is not necessary for the electric vehicle to travel a long distance, the sub-battery may be disconnected from the vehicle body; in this case, the electric vehicle is reduced in weight as much, and is improved in mobility, and the energy usage otherwise required for carrying the sub-battery is eliminated. When driving the motor, the electric power of the sub-battery is preferentially used. Therefore, if the sub-battery which is emptied of its change earlier is removed, then under the condition that the vehicle weight is reduced, the traveling can be continued with the electric power of the main battery, so that the total traveling distance is further increased. In addition, when of the motor, regenerates electrical energy during braking. The main battery is preferentially charged by the regenerative power. Therefore, with the electric power of the main battery maintained unchanged, the traveling distance is maximumly increased after the sub-battery is removed. Furthermore, when the main battery is emptied, before the completion of the charging of the main battery the traveling can be started with the sub-battery coupled to the vehicle body.
Preferably, in the electric vehicle, the driving of the motor by the main battery is started after the sub-battery has been completely discharged.
In the electric vehicle thus designed, after the sub-battery has been completely discharged, the driving of the motor with the main battery is permitted. Therefore, while the power of the main battery is being maintained unchanged, the power of the sub-battery is effectively used to the last. Thus, the traveling distance of the electric vehicle is increased as much.
The state that the sub-battery has been completely discharged is not limited to the state that the left-quantity of the sub-battery has become 0%; that is, it may be the state that the sub-battery has a predetermined left-quantity with which the damage of the sub-battery by over-discharge is avoided.
Preferably, in the electric vehicle, the charging of the sub-battery by the regenerative power is started after the main battery has been completely charged.
In the electric vehicle thus designed, the charging of the sub-battery by the regenerative power is permitted after the main battery has been completely charged. Hence, the traveling distance is increased with the main battery maintained completely charged.
The state that the main battery has been completely charged is not limited to the state that the left-quantity of the main battery has become 100%; that is, it may be the state that the main battery has a predetermined left-quantity with which the damage of the main battery by over-charge is avoided.
Preferably, in the electric vehicle, the sub-battery is mounted on a trailer which is detachably coupled to the vehicle body.
Hence, in the electric vehicle thus designed, it is unnecessary to provide a space for setting the sub-battery. Hence, the degree of freedom in the design of a vehicle body is improved as much, and without great modification the existing electric vehicle can be used as it is. Furthermore, since the sub-battery is mounted on the trailer, a battery of large capacity can be used with no trouble, and merely by connecting the trailer to the vehicle body, the connection of the sub-battery can be readily achieved.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with attached drawings.